WorldWind Kotlin/earth.worldwind.layer.buildings/OverpassBuildingsSource

OverpassBuildingsSource

class OverpassBuildingsSource(val endpoint: String = "https://overpass-api.de/api/interpreter", val timeout: Int = 25) : TiledFeatureSource

Fetches OSM building footprints from a public Overpass API endpoint.

One request per Sector is issued, returning all ways tagged either building=* or building:part=* whose geometry is inside the bbox. Parts are emitted alongside their parent shell (Overpass unions de-dupe by id, so a way tagged both ways still appears once); each part has its own height/min_height, so a tower-on-podium reads as two stacked volumes without any extra assembly logic.

Multipolygon (relation-based) buildings are intentionally not assembled here — they are rare for buildings and would require a second round-trip; callers needing them can layer a relation-aware source on top of this one.

Heights are derived via OsmHeight.resolve; coordinates are emitted as Positions with the top-altitude pre-baked, ready for OsmBuildingsLayer to wrap in an extruded earth.worldwind.shape.Polygon with earth.worldwind.geom.AltitudeMode.RELATIVE_TO_GROUND.

Parameters

endpoint

Overpass-compatible HTTP endpoint. Defaults to the public main instance — for production use, route to a self-hosted mirror to respect fair-use limits.

timeout

Per-request Overpass timeout, also wired into the QL [timeout:N]; header.

Constructors

OverpassBuildingsSource

constructor(endpoint: String = "https://overpass-api.de/api/interpreter", timeout: Int = 25)

Types

Companion

object Companion

Properties

endpoint

val endpoint: String

timeout

val timeout: Int

Functions

open override fun close()

Release any resources held by the source (HTTP client, etc.). Idempotent default no-op.

fetchTile

open suspend override fun fetchTile(z: Int, x: Int, y: Int, sector: Sector): Flow<CachedFeatureRow>?

tryReadCachedTile

open suspend fun tryReadCachedTile(z: Int, x: Int, y: Int, sector: Sector): Flow<CachedFeatureRow>?

Cache-only fast-path read for (z, x, y). Default returns null — a plain network source has no cache to consult. Cache-backed sources override to read their store without going through the network-fetch concurrency budget. Empty flow is the negative-cache sentinel ("fetched, no features"); null is a true miss.